Alternating current bell



Dec. 22, 1964 F. E. WELD 3,162,850

ALTERNATING CURRENT BELL Filed Sept. 21, 1961 2 Sheets-Sheet 1 FIG. I 9

JNVENTOR. FOSTER E. WE LD 30 U ATT RNEYS Dec. 22, 1964 F. E. WELD3,162,850 ALTERNATING CURRENT BELL Filed Sept. 21, 1961 2 Sheets-Sheet 2FIG. 3

5| cycle i l V T :08 i I FIG. 4 T? Current 2s Y 29 I 78 INVENTOR 68FOSTER E, WELD FIG. 5

ATTORNEYS United States Patent 3,162,859 ALTERNATENG (IURRENT BELLFoster E. Weld, Newton Highlands, Mass assignor, by mesne assignments,to E. W. Bliss Company, Canton, ()hio, a corporation of Delaware FiiedSept. 21, 1361, Ser. No. 139,652 2 Ciaims. (Cl. 349-699) The presentinvention relates generally to bells of the type having a vibratingstriker for actuation by alternating current, and more particularly to abell that strikes at half the frequency of the energizing currentwithout the use of current-interrupting electrical contacts.

An object of this invention is to provide a bell adapted for use ininstallations including fire alarms, industrial signal application,program dismissal systems in schools and other installations wherealternating current power is supplied.

Hitherto, one of the means used to achieve vibration of the striker inalternating current bells has consisted of make and break contactelements for interruption of the electrical current supplied to astriker actuating solenoid. These contact elements are a mapor source ofdifficulty in maintenance because of imperfect electrical connectionbetween the elements caused by dint or the like, corrosion and contactwear. In many applications bells are subjected either to the weather orto other conditions whereby water, smoke, corrosive gases and foreignmatter may reach the contact elements and result in faulty operation.Also, even under ideal conditions the opening and closing of electricalcontact elements produces radio and television reception interference.Accordingly, a second object of this invention is to provide a bellwhich does not depend for its operation upon electrical contactelements.

A common alternating current power frequency is 60 cycles per second.Hitherto, most bells adapted for operation at this frequency have beenof a type producing one heat per cycle with gong shells of from aboutfour to ten inches in diameter. This frequency is con sidered too greatfor a clear, pleasant-sounding ring. Accordingly, a third object of thisinvention is to provide a bell adapted for operation at a givenenergizing frequency, but striking the gong at a lower frequency atwhich a more satisfactory ring is obtained.

A further object is to provide a bell mechanism of a type characterizedby a high speed of response in starting and stopping upon the initiationand interruption of the actuating current.

With the foregoing and other objects hereinafter described in view, afeature of this invention resides in the provision of a strikingmechanism actuated by an electromagnet in association with a permanentmagnet to produce a gong striking frequency equal to half thealternating current frequency applied.

Another object of the invention is the provision of a bell mechanism ofthe type described including a readily and cheaply fabricated fixedassembly portion of a magnetic circuit, said fixed assembly including acoil or solenoid, a polarizing permanent magnet and pole pieces.

Another feature resides in the provision of a pair of magnetic circuitshaving a common leg including the oscillating striker mechanism.

A further feature resides in the provision of a bell having theforegoing features while at the same time having the actuating mechanismtotally disposed within the gong in a weather-proof assembly.

A still further feature resides in the provision of ad justment meansfor the striker mechanism to insure a quick response upon the initiationand interruption of energizing current and to control the force ofstriking the "ice gong to insure a pleasing tone with the desireddistance carrying power.

Other features of the invention reside in certain details ofconstruction, assemblies and arrangements of the parts and modes ofoperation that will be more clearly understood from the followingdescription of a preferred em ibodiment, having reference to theappended drawings in which:

FIG. 1 is a central vertical longitudinal section;

FIG. 2 is a vertical radial section taken on line 2-2 FIG. 1;

FIG. 3 is a horizontal longitudinal section taken on line 33 of FIG. 1rotated counterclockwise from that of FIG. 1;

FIG. 4 is a composite time curve and schematic diagram illustrating therelationship between the actuating alternating current frequency and thegong striking frequency; and

FIG. 5 is a fragmentary View similar to FIG. 1 illustrating amodification of striker actuating means.

Referring to the drawings, there is provided a cast metal base 12 whichis of dished shape and provided with a boss 14 to support a dish shapedmetal gong 16. The base 12 is step-shaped to provide annular shoulders18 and 21? between which there is disposed a cylindrical portion 22. Agong mounting screw 24 is threaded into a hole in the boss 14 which liesin the central axis of the base. This screw is provided with a flangedeccentric bushing 26 and a resilient sealing washer 23. The bushing 26has an annular surface 29 eccentric to the screw axis which fits in acircular hole through and coaxial with the gong 16. This arrangementpermits lateral adjustment of the axis of the gong in relation to theaxis of the base while maintaining these axes in parallel relationship.This adjustment changes the space between the gong and a non-magneticstriker rod 30 which is suported within the cylindrical portion 22 ofthe base and constrained to move in a direction transversely of the axisof the base and gong. After adjustment by rotation of the bushing 26,the screw 24 may be tightened to clamp the gong in position whereuponthe washer 23 provides a weather tight seal for the opening through thegong.

The base 12 has a flange portion 32 having an annular lip 34- extendingrearwardly of the gong and an inwardly-facing shoulder 36 to provide aseat for an annular gasket 38. The base, in conjunction with the gasket38, is adapted for sealed mounting upon a cast junction box 4i) having atapped hole 42 for a conventional electrical cable or conduitconnection. The box 40 is provided with a plurality ofinwardly-projecting integral bosses forming screw suports 44 each ofwhich is disposed parallel to the central axis of the box 4% and boredand tapped to receive a mounting screw 46. The screws 46 secure a flatcircular metal receptacle mounting plate 48 in a plane at right anglesto the central axis of the box. The plate 48 supports an insulatingprong receptacle 5% in position to receive a pair of prongs 52 supportedby the base 12 and extneding rearwardly of the gong. It will beunderstood that a pair of wires (not illustrated) is led from anexternal power source to the box 40 and connected with receptacle Si ina conventional manner to provide a circuit for the bell through theprongs 52. The prongs are inserted in the receptacle 50 as the base 12is placed in position upon the box 40. The base is held securely on thebox 443 by a pair of clamps 54 (FIG, 3) received over the flange portion32 of the base and an annular flange 56 on the box 40, the flange 56having a rearwardly-extending sloping surface matching a surface of theclamps 54-. A pair of mounting screws 53 provided with split lockwashers 60 are threaded through holes in has a central integral portion92 of larger diameter.

' associated magnetic actuating parts are shown secured to the base 12by a pair of bolts 62 preferably of nonmagnetic material. The headsofthese bolts are received in recesses in the base 12 with resilientsealing Washers 6 4 which provide a weather-tight seal for the holes inthe base. The base is provided with a pair of bosses 66 projectingrearwardly of the gong against one of which is secured by aform-magnetic pole piece 68. An electromagnet coil 78 is received overone ofthe bolts 62 and against this pole piece. A pair of permanentmagnetic slugs 72, preferably provided with circular metallic backingplates 73 in the case of ceramic slugs, and preferably ferro-magneticcylindrical spacers 74 are placed over the other bolt 62. The axiallength of the coil 7% is preterably equal to the sum of the axiallengths of the slugs '72, the backing plates '73 and the spacers '74. Itwill be understood that while two magnetic slugs are illustrated, fewerora greater number of slugs may be assembled on the bolt, depending uponthe residual magnetic strength of the slugs employed and the size of thegong to be used. To facilitate this modification, each of the spacers 74is preferably .of the same axial thickness as one individual slug.

A second pole piece 78 which is preferably substantially identical tothe pole piece 68 is received over the bolts 62. Insulation plates 8%spaced by suitable washers 82 are placed over the pole piece 78 and areprovided with holes through which the bolts e2 are passed. Nuts 84 arethreaded on the bolts s2 and tightened to form a rigid assembly. Theplates 3% thereby form clamps for tangs 86 integral with and extendingat right angles from the prongs 52 (FIG. 1). The tangs 86 projectradially outwardly between the plates 8% (FIG. 1) to provide solderlugs, each lug being connected by a wire (not shown) to one terminal ofthe electromagnct 7%. The pole piece 7?; which is provided with acentral opening 88 (PEG. 2) incycle, that is, only once every twocycles.

d springs preferably having identical'spring' characteristics and beingopposed to one another. When the bell is in the unactuated condition,the initial compression of each spring is added to the attraction whichthe permanent magnetic field exerts on the respectiveadjacent plate 94,and the sums of these two forces represent equal and opposed rcsultantsat the top and bottom of the rod.

A further feature of the foregoing adjustment is that the position ofthe striker rod is arranged to bring one of the plates 94 slightlycloser to its associated projections ht? than in the case of the otherplate. With the foregoing adjustments, the bell is in condition foractuation. FIG. 4 illustrates the currentin the elcctromagnet 70 as afunction of time when an alternating potential is applied between theprongs 52. In the lower part of this figure the striker rod Ellis shownschematically in corresponding relation to the gong 16 at time intervalsof one-fourth cycle. It will be noted that the gong is struck only atthe alternate positive. peaks of the current This operation will next'beexplained in further detail.

As viewed in FIGS. 1 and 2, the upper plate 94 is is adjusted to becloser to-its associated pole projections 90 than'is the lower plate 94,assuming'the current is 0E. The operation is as shown'in H6. 4 ifcurrent is applied at time t=G and if the first half-cycle of currentinduces a polarity in the electromagnet 7%) which aids the permanentmagnetic field in attracting the upper plate toward sulates thecomponents of the magnetic circuits from the prongs 52 and tangs 86.

The pole pieces 6% and 7d are each provided with integral fiataxially-extending right angle projections t which face one another inpairs. Space'is provided hetween'these projections for the striker rod36 which A pair of flat circular ferromagnetic plates 94 are slidinglyreceived against the shoulders of the portion 2 and extend radially ofthe striker rod 39 so that the surfaces of the plates are in opposedrelationship tothe projections 96 of the pole pieces.

To mount reciprocably therod 3t threaded plugs )6 and 98 arereceived intapped holes in the cylindrical portion 22 of the base 12. The plug 93has a full-length drilled axial hole to receive the striking end of therod 39. A portion of this hole is relieved to receive a closely fittedbushing 1% having a low coefiicient of friction with the rod 3! slidabletherein. The plug 96 has a blind axial hole to receive the opposite endof the rod it this hole being similarly relieved to receive a bushing1&2 for the rod. As shown for plug 96, these plugs have a screw slot 134- for radial adjustment of the plug.

The plugs as and 98 have inwardly projecting shouldered extensions toreceive tapered compression springs 1556 bearing at their opposite endsagainst the plates 5 4.

In operation, initial adjustments of the plugs are made to control boththe axial distance between the plugs and the axial distance of eachplugr'rorn tbe central axis of the screw'fi l. It will be understoodthat this latter axis is also the central axis of the base 12 and of themagnetic circuit defined by the pole pieces. it will also be understoodthat the foregoing adjustment controls the initial com ression of eachof the springs the, these the pole projection. In the first half-cyclethe striker,

alreadybeingclose to the gong, strikes it and the upper plate M strikesor projections 9t The current in the electroniagnet ill thenbegins todecrease and the lower spring 1% begins to move the striker upwardly. Asthe upper plate 94 moves further from the upper projections 96 the airgap is increased,

reaches its closest position to the upper thus increasing the magneticreluctance of the path through this plate and further decreasing theattractive force of the magnetic fields on it. In the secondhalf of-thefirst cycle the current reverses and produces a magnetic field inopposition to the permanent magnet, thus still further reducing thetotal field acting uponrthe upper plate 94.

At the beginning of the second cycle, the current again produces anaiding magnetic field, but at that time the upper plate he is furtherfrom the projections 96 than it was in the first cycle, and accordinglythe ficlds I have a relatively smaller eflect on that plate. On theother hand, the lower plate @4 is relatively closer to its projectionsand the aiding fields draw it upwardly.

conclusion of one-fourth of the third cycle. the :striker again strikesthe gong 16' Referring to PlGURE 5, there is illustrated anotherembodiment which utilizes only one armature or circular plate 94, andmodified pole pieces 68 and '73. Y The bell according to this embodimentis also self-starting and, in addition, has increased plunger travel forincreased sound output. The absence of the lower armature and the use ofmodified polerpieces r58, 73' substantially reduce the effectiveness ofthe attractive forces operating on the lower end of the striker rod 36and permits long striker travel without altering the air gap between theupper plate $4 (FIGURE 1) and the upper ends of pole pieces 6,8, 73.

As showniin FIGURE 5, the lower axially-extending projections 9% fromeach of the pole pieces as, 73 have been omitted to form pole pieces 63,78. Accordingly, pole pieces 68', 78' have each only oneaxially-extending projection 96 which corresponds to the upperprojection 96 shown in FIGURE 1. It should be understood that whereupper and lower springs are similar, the central I! 3 portion 92 ofstriker rod 30 will be extended a distance equal to the thickness of theabsent plate 94. The lower spring 186 arranged in FIGURE 5 to bearagainst the lower shoulder of central portion 92, while the upper spring106 (FIGURE 1) bears against upper plate 94. The relationship of upperplate 94 to the upper pair of projections 90 is maintained as in theembodiment of FIGURES 1-3. The embodiment utilizing one plate 94 and themodified pole pieces 68', 78 also provides a bell whose operation issubstantially as described for the embodiment utilizing two plates 94and pole pieces 68, 78.

It will be appreciated that the spring rates are chosen in relation tothe size of the magnetic fields so that sufficientamplitude of motion ofthe striker and the plates 94 is obtained. Spring tension and the weightof the moving parts are chosen to be such that the natural frequency ofvibration of the moving parts is 30 cycles per second, for bestopenation of the bell.

It will also be seen that the striking frequency will be thirty strokesper second if the applied current is sixty cycles per second whichproduces a pleasing tone in contrast with a sixty stroke rate.

The described embodiment is protected from the weather and since noelectrical contacts are required, no interference to radio or televisionreception will occur and the bell will give dependable performance witha minimum of maintenance.

It will be understood that numerous variations in the describedstructure of the bell may be provided to adapt the mechanism to gongs ofvarying diameter and to alter the structure and relationships of thepants for various purposes consistently with the modes of operation andteachings herein described. These adaptations and variations may becarried out without departing from the spirit and scope of thisinvention.

What is claimed is:

1. In an alternating current bell, in combination: a base; gong meansmounted on said base; a striker rod resiliently mounted on said base foroscillatory movement for striking said gong, said striker rod having atleast one plate secured thereto and movable therewith, said plateextending outwardly from said striker rod; magnetic circuit meansmounted on said base for imparting said oscillatory movement to saidstriker rod, including an electromagnet, a permanent magnet, and twopole elements; each said pole element comprising a vertical element andat least one arm horizontally extending from an end thereof, said poleelements secured to said base with said horizontal arms in spaced apartand opposed relation to each other; said electromagnet and permanentmagnet secured to said base and located substantially equally betweensaid poles; opposed striker rod biasing spring means for urging said rodto a normal position with said plate spaced from said arms; whereby whensaid magnetic circuit means is energized by alternating current saidstriker rod means will oscillate and strike said gong at a frequencysubstantially below that of the ternating current applied to energizesaid magnetic circuit means.

2. In an alternating current bell as set forth in claim 1, wherein thebias of said spring means and mass of said rod and plate is selected totune the same to half the frequency of said alternating current.

References Cited in the file of this patent UNITED STATES PATENTS1,134,758 North Apr. 6, 1915 1,815,853 Lake July 21, 1931 1,839,342Richmond June 5, 1932 2,205,189 Edwards lune 18, 1940 2,220,979 SwansonNov. 12, 1940 2,463,380 Harris Mar. 1, 1949 2,683,871 Meleski July 13,1954 2,854,660 Best et a1 Sept. 30, 1958

1. IN AN ALTERNATING CURRENT BELL, IN COMBINATION: A BASE; GONG MEANSMOUNTED ON SAID BASE; A STRIKER ROD RESILIENTLY MOUNTED ON SAID BASE FOROSCILLATORY MOVEMENT FOR STRIKING SAID GONG, SAID STRIKER ROD HAVING ATLEAST ONE PLATE SECURED THERETO AND MOVABLE THEREWITH, SAID PLATEEXTENDING OUTWARDLY FROM SAID STRIKER ROD; MAGNETIC CIRCUIT MEANSMOUNTED ON SAID BASE FOR IMPARTING SAID OSCILLATORY MOVEMENT TO SAIDSTRIKER ROD, INCLUDING AN ELECTROMAGNET, A PERMANENT MAGNET, AND TWOPOLE ELEMENTS; EACH SAID POLE ELEMENT COMPRISING A VERTICAL ELEMENT ANDAT LEAST ONE ARM HORIZONTALLY EXTENDING FROM AN END THEREOF, SAID POLEELEMENTS SECURED TO SAID BASE WITH SAID HORIZONTAL ARMS IN SPACED APARTAND OPPOSED RELATION TO EACH OTHER; SAID ELECTROMAGNET AND PERMANENTMAGNET SECURED TO SAID BASE AND LOCATED SUBSTANTIALLY EQUALLY BETWEENSAID POLES; OPPOSED STRIKER ROD BIASING SPRING MEANS FOR URGING SAID RODTO A NORMAL POSITION WITH SAID PLATE SPACED FROM SAID ARMS; WHEREBY WHENSAID MAGNETIC CIRCUIT MEANS IS ENERGIZED BY ALTERNATING CURRENT SAIDSTRIKER ROD MEANS WILL OSCILLATE AND STRIKE SAID GONG AT A FREQUENCYSUBSTANTIALLY BELOW THAT OF THE ALTERNATING CURRENT APPLIED TO ENERGIZESAID MAGNETIC CIRCUIT MEANS.